Use of indium in manufactured materials may be increasing in certain electronic devices such as flat panel displays. Studies in experimental animals and human case reports indicate that indium tin oxide may cause pulmonary disease in humans. The International Agency for Research on Cancer (IARC) has classified indium phosphide as probably carcinogenic to humans (Group 2A) based on a determination of sufficient evidence of carcinogenicity in experimental animals. Limited information is available on the actual users of indium compounds in the U.S. and the potential for occupational exposure among these users. Information on likely downstream users of indium is especially needed in order to conduct more systematic informational surveys of potential indium users, to identify candidate companies for exposure assessment measurements, and to estimate the number of indium-exposed workers. Information on indium use in the U.S. is so limited that basic fact-finding and networking needs to be done to determine if occupational exposure monitoring studies in the U.S. are both warranted and feasible at this time. Before a systematic survey can be conducted to identify and characterize indium-using companies for exposure monitoring studies and to estimate number of potentially-exposed workers, we need better information on which industry groups should be the focus of the survey and the work process/job questions that will elicit information on number of potentially-exposed workers. NIOSH has initiated a number of activities to address these data needs. A number of valuable contacts were made at the annual meeting of the Semiconductor Environmental Safety and Health Association with health and safety professionals in the semiconductor and solar industries, as well as with researchers at Federal laboratories involved in solar research, solar health and safety, or life cycle analysis of indium. An outgrowth of these contacts was an initiative by the Semiconductor Industry Association to administer a brief (6-question) survey developed by NIOSH to its member companies about the use of indium compounds at their facilities. NIOSH has also been contacting possible indium-using companies across the potential spectrum of indium users, initially by letter, followed by telephone or e-mail contact to obtain additional information. Several facilities have agreed to site visits. NIOSH will continue contacting potential indium-using companies and expand this project into a exposure assessment in FY 2010. NIOSH has also been in contact with a graduate student at MIT who is studying the environmental life cycle of indium, including natural and industrial contributions. As a result of these ongoing efforts, NIOSH will have a better understanding of the use of indium and indium compounds in the workplace.